Change to latest rubyspec reference

spec/integrations.yml

@@ -2,35 +2,13 @@
 - name: rubyspec
   namespace: Rubyspec
   repo_uri: 'https://github.com/ruby/rubyspec.git'
-  repo_ref: 249a36c2e9fcddbb208a0d618d05f6bd9a64fd17
+  repo_ref: 59bdcb4ea95c60159bb2bfc8c73022364da8ec0d
   integration_name: mspec
   mutation_coverage: false
   mutation_generation: true
   exclude:
-    - command_line/fixtures/bad_syntax.rb
-    - command_line/fixtures/freeze_flag_required_diff_enc.rb
-    - core/file/stat_spec.rb
-    - core/kernel/shared/sprintf_encoding.rb
-    - core/module/fixtures/autoload_empty.rb
-    - core/module/fixtures/autoload_never_set.rb
-    - core/module/fixtures/path2/load_path.rb
-    - core/regexp/shared/new.rb
-    - core/string/casecmp_spec.rb
-    - core/string/encode_spec.rb
-    - core/string/inspect_spec.rb
-    - core/string/shared/to_sym.rb
-    - core/symbol/casecmp_spec.rb
-    - language/fixtures/freeze_magic_comment_required_diff_enc.rb
-    - language/fixtures/utf16-be-nobom.rb
-    - language/fixtures/utf16-le-nobom.rb
-    - language/predefined/fixtures/data4.rb
-    - language/predefined/fixtures/data_only.rb
-    - language/source_encoding_spec.rb
-    - library/base64/decode64_spec.rb
-    - library/cgi/escapeHTML_spec.rb
-    # invalid regexp on 3.1 parser
-    - regexp_parser/test/parser/test_escapes.rb
-    - security/cve_2010_1330_spec.rb
+  # regexp_parser crash
+  - language/regexp/back-references_spec.rb
 - name: regexp_parser
   namespace: Regexp
   repo_uri: 'https://github.com/ammar/regexp_parser.git'

spec/support/corpus.rb

@@ -135,7 +135,12 @@ def checkout
       #
       # @return [Integer] mutations generated
       def check_generation(path)
-        node = Unparser.parse(path.read) or return 0
+        begin
+          node = Unparser.parse(path.read) or return 0
+        # no need to generate mutation if the source is invalid
+        rescue Parser::SyntaxError
+          return 0
+        end
 
         mutations = Mutant::Mutator::Node.mutate(
           config: Mutant::Mutation::Config::DEFAULT.with(operators: Mutant::Mutation::Operators::Full.new),